net.ontopia.topicmaps.nav2.plugins.PluginContentHandler.java Source code

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Here is the source code for net.ontopia.topicmaps.nav2.plugins.PluginContentHandler.java

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/*
 * #!
 * Ontopia Navigator
 * #-
 * Copyright (C) 2001 - 2013 The Ontopia Project
 * #-
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * !#
 */

package net.ontopia.topicmaps.nav2.plugins;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import net.ontopia.topicmaps.nav2.core.NavigatorApplicationIF;
import net.ontopia.xml.SAXTracker;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;

/**
 * INTERNAL: A Content Handler for reading in a Plug-in Configuration
 * file (plugin.xml) which contains detailed information about one (or
 * more) Plug-in(s).
 *
 * @see net.ontopia.topicmaps.nav2.plugins.PluginIF
 */
public class PluginContentHandler extends SAXTracker {

    // Define a logging category.
    private static final Logger log = LoggerFactory.getLogger(PluginContentHandler.class.getName());

    // constants
    public static final String PLUGINS_ROOTDIR_PLACEHOLDER = "${" + NavigatorApplicationIF.PLUGINS_ROOTDIR_KEY
            + "}";

    // member
    private Collection plugins;
    private PluginIF cplugin;
    // This does not contain the context-path, but only "/plugins/"
    private String pluginsRootURI;

    private String param_name;

    public PluginContentHandler(String pluginsRootURI) {
        this.pluginsRootURI = pluginsRootURI;
        keepContentsOf("title");
        keepContentsOf("descr");
        keepContentsOf("target");
        keepContentsOf("activated");
        keepContentsOf("uri");
        keepContentsOf("parameter");

        plugins = new ArrayList();
    }

    public Collection getPlugins() {
        return plugins;
    }

    // --------------------------------------------------------------
    // override methods from SAXTracker
    // --------------------------------------------------------------

    @Override
    public void startElement(String nsuri, String lname, String qname, Attributes attrs) throws SAXException {
        super.startElement(nsuri, lname, qname, attrs);

        if ("plugin".equals(qname)) {
            String klass = attrs.getValue("class");
            if (klass == null)
                cplugin = new DefaultPlugin();
            else
                cplugin = createPlugin(klass);

            if (cplugin == null)
                return; // createPlugin may fail...

            cplugin.setId(attrs.getValue("id"));
            String str_groups = attrs.getValue("groups");
            // split group containing string into elements
            if (str_groups != null && !str_groups.equals("")) {
                String[] grpArray = StringUtils.split(str_groups, ",");
                List groups = new ArrayList(grpArray.length);
                for (int i = 0; i < grpArray.length; i++)
                    groups.add(grpArray[i].trim());
                cplugin.setGroups(groups);
            }

        } else if ("parameter".equals(qname)) {
            param_name = attrs.getValue("name");
            if (attrs.getValue("value") != null)
                cplugin.setParameter(attrs.getValue("name"), attrs.getValue("value"));
        }
    }

    @Override
    public void endElement(String nsuri, String lname, String qname) throws SAXException {
        super.endElement(nsuri, lname, qname);

        if ("plugin".equals(qname))
            plugins.add(cplugin);
        else if ("title".equals(qname))
            cplugin.setTitle(content.toString());
        else if ("descr".equals(qname))
            cplugin.setDescription(content.toString());
        else if ("target".equals(qname))
            cplugin.setTarget(content.toString());
        else if ("uri".equals(qname))
            cplugin.setURI(processURI(content.toString()));
        else if ("activated".equals(qname)) {
            String value = content.toString();

            if (cplugin.getState() != PluginIF.ERROR) {
                if (value == null || !value.equals("yes"))
                    cplugin.setState(PluginIF.DEACTIVATED);
                else
                    cplugin.setState(PluginIF.ACTIVATED);
            }
        } else if ("parameter".equals(qname)) {
            // If parameter hasn't yet been set use the content of the parameter element.
            if (cplugin.getParameter(param_name) == null)
                cplugin.setParameter(param_name, content.toString());
            // Reset parameter name member
            param_name = null;
        }
    }

    // --------------------------------------------------------------
    // internal helper methods
    // --------------------------------------------------------------

    private PluginIF createPlugin(String klass) {
        try {
            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
            Class pclass = Class.forName(klass, true, classLoader);
            return (PluginIF) pclass.newInstance();
        } catch (ClassNotFoundException e) {
            log.error("Couldn't find class of plugin " + klass + ": " + e.getMessage());
            PluginIF plugin = new DefaultPlugin();
            plugin.setState(PluginIF.ERROR);
            return plugin;
        } catch (InstantiationException e) {
            log.error("Couldn't instantiate plugin (" + klass + "): " + e.getMessage());
        } catch (IllegalAccessException e) {
            log.error("Couldn't access plugin instance " + klass + ": " + e.getMessage());
        } catch (NoClassDefFoundError e) {
            log.error("Couldn't find class definition of plugin " + klass + ": " + e.getMessage());
        }
        return null;
    }

    /**
     * INTERNAL: Process specified URI string and replace placeholder
     * (<code>"${" + NavigatorApplicationIF.PLUGINS_ROOTDIR_KEY +
     * "}"</code>) with actual plugins root directory.
     */
    private String processURI(String orig_uri) {
        String uri = orig_uri;
        if (uri.indexOf(PLUGINS_ROOTDIR_PLACEHOLDER) >= 0) {
            uri = StringUtils.replace(uri, PLUGINS_ROOTDIR_PLACEHOLDER, pluginsRootURI);
        }
        return uri;
    }

}